@klodianimeri/pipejs/src/pipes/is-subset-of.ts

Pipe functions that provide convenient and efficient ways to work with iterators.

import { Pipe } from "../pipe.js";
import { assertSync, Done, Yield } from "../util/index.js";

export function isSubsetOf(source: Iterable<any, any, unknown>): Pipe {
    assertSync(source);

    return () => {
        let sourceSet: Set<any> = source instanceof Set ? source : new Set<any>(source);
        return (result: IteratorResult<any>): Array<IteratorResult<any>> => {
            if (result?.done) {
                return [Yield(true), result];
            }

            if (!sourceSet.has(result.value)) return [Yield(false), Done()];
        };
    }
}